It’s expected to be a cold night across Maine, and the south-central portion of the state is under a frost advisory between midnight Friday and 8 a.m. Saturday.

Kennebec and Androscoggin Counties, central Cumberland County and interior York County fall under the advisory issued by the National Weather Service.

Temperatures are expected to plunge to around 34-35 degrees in those areas, Stephen Baron, a meteorologist at the weather service office in Gray, said on Friday. The southern coastline, where temperatures are projected to hover in the high 30s, does not fall under the frost advisory.

While it is technically late in the season for southern Maine to reach such temperatures — hence the warning — it’s not uncommon for the area to see frost advisories in early May, Baron said.

According to weather service forecasts, parts of western and northern Maine are projected to be even colder Friday night into Saturday. However, Baron explained that the weather service does not begin declaring frost advisories in those regions until later in May.

“Those are climatologically later, so we don’t issue the (advisories) until later,” he said.

A trough over the northeast part of the country, coupled with northwesterly winds, is creating a “cold air advection,” which means cold air is being pushed into Maine, Baron explained.